Lucile Dianne's PhD thesis

Characterization of the role of the acanthocephalan parasite Pomphorhynchus laevis non-infective larval stage in the behavioural manipulation of its amphipod intermediate host

Defended on the 6th December 2012

Funding: CNRS / région Bourgogne

Supervisors: Thierry Rigaud and Marie-Jeanne Perrot-Minnot

Started in October 2009



In trophically-transmitted parasites, exploitation strategies of the intermediate host have been selected, in a way increasing parasites transmission probabilities to their definitive host. Particularly, numerous parasites are able to alter their intermediate host behaviour, a phenomenon called ‘behavioural manipulation’. This manipulation only occurs when the parasite developmental stage (or larval stage) is infective for the definitive host. Before reaching this stage, the development of parasite larvae is not sufficiently advanced to allow establishment in the definitive host (this stage is thus called ‘non-infective’). Early transmission of a non-infective stage therefore implies parasite death. Parasites able to reinforce their intermediate host anti-predatory defences when non-infective (i.e. protecting them from predation), before manipulating their intermediate host behaviour when infective (i.e. exposing them to predation by definitive hosts), should have been selected. In this thesis, I showed that, when non-infective, the acanthocephalan parasite Pomphorhynchus laevis strengthens its amphipod intermediate host anti-predatory defences, which diminishes its host predation risk. This protective-like strategy negatively affects the amphipod food intake, although it has no effect on host energetic reserves. Similarly, the male amphipod reproductive behaviour is not affected by infection with a non-infective stage of the parasite. The origins of such parasitic strategy are discussed, and ecological perspectives to this host behavioural change are suggested.



Loïc Bollache, Professeur, Université de Bourgogne, président
Jacob Koella, Professeur, Université de Neuchâtel (Suisse), examinateur
Yannick Outreman, Professeur, Agrocampus Ouest, Rennes, rapporteur
Marie-Jeanne Perrot-Minnot, Maître de conférences, Université de Bourgogne , directeur
Thierry Rigaud, Directeur de recherches CNRS, Dijon, directeur
Ana Rivero, Chargée de recherches CNRS, Montpellier, examinateur
Frédéric Thomas, Directeur de recherches CNRS, Montpellier, rapporteur